1. Field of the Invention
The invention relates to an electronic apparatus system and its charge control method. More particularly, the invention relates to an electronic apparatus system in which an electronic apparatus, an expansion device, and a battery pack are constructed so as to be freely joined and, each have separated (detachable) and a charging function, and to its charge control method.
2. Related Background Art
Hitherto, in order to expand the function of a notebook-sized personal computer or the like, as shown in FIG. 2, a system in which a personal computer (hereinafter, simply referred to as a computer) 1' is combined with an expansion device 2' having therein an FDD, an HDD, or an expansion board or the like by connection of a connector (computer side connector) 3' and a connector (expansion device connector) 4', and two batteries 5' and 6' can be built in the computer 1' permitting operation for a long time has been proposed.
When the batteries 5' and 6' are charged, energy from an AC adapter 7' is supplied to the computer 1' through the connectors 3' and 4', thereby charging the batteries by a charging circuit (not shown).
The conventional personal computer is constructed so that a desk-top type personal computer is separated into a notebook-sized personal computer and an expansion device. The expansion device is designed on the assumption that it is used in a desktop manner as a prerequisite, and its size is large.
However, in the notebook-sized personal computer or the like, it is a present situation that importance is paid to portability and necessary minimum functions are provided for the computer, and thus, a compact size is realized, thereby paying importance to not the portability of only the personal computer itself but also the portability of the computer even when combined with the expansion device. A function to charge with good operability a state of the personal computer, alone the expansion device alone, and the combination of both, is necessary.